deps: update black requirement from >=24.4.0 to >=26.5.1

Updates the requirements on [black](https://github.com/psf/black) to permit the latest version.
- [Release notes](https://github.com/psf/black/releases)
- [Changelog](https://github.com/psf/black/blob/main/CHANGES.md)
- [Commits](psf/black@24.4.0...26.5.1)

---
updated-dependencies:
- dependency-name: black
  dependency-version: 26.5.1
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements.txt

@@ -12,7 +12,7 @@ yagmail
 openpyxl>=3.1.5
 timezonefinder
 pre-commit>=4.6.1
-black>=24.4.0
+black>=26.5.1
 isort>=8.0.1
 flake8>=7.0.0
 pytest>=7.4.0